<nav>
  <a [routerLink]=" ['/collection'] " [ngClass]="{clickOn: !isListPage}">
    <i>收藏</i>
  </a>
  <a [routerLink]=" ['/list']" [ngClass]="{clickOn: isListPage}">
    <em></em>
    <i>通讯录</i>
  </a>
</nav>
